Field
The described technology generally relates to a system for transmitting and receiving image data, and more particularly, to a system for transmitting and receiving various kinds of image data including ultra-high definition (UHD) image data.
Description of the Related Technology
A mobile broadcast service which is low in resolution needs a high definition (HD) class broadcast service, and moreover, requirements for a full HD. UHD (4K, 8K, etc.) broadcast service are rapidly increasing. Therefore, requirements for technology that efficiently transmits and receives broadcast data in a fixed environment and a mobile environment are increasing.
In particular, UHD televisions (TVs) are attracting attention as a next generation broadcast service that provides a multichannel (ten or more channels) audio service and a UHD image service for providing image quality which is four to sixteen times sharper than image quality provided by HD TVs. However, in current domestic UHD TV technology, development of relevant apparatuses other than display devices of UHD TVs is inadequate.
Moreover, technology for coding UHD image data is in a state where after high efficiency video coding (HEVC) which is standard technology is finished in 2013, a formal coding product to which HEVC technology is capable of being applied is not developed.
The HEVC is next-generation image compression technology which has a compression rate higher than and a complexity lower than H.264/AVC technology, and is attracting attention as core technology for effectively compressing massive data of an HD class image and an UHD class image.
The HEVC performs block-unit coding like conventional compression standards. However, since there is only one profile, the HEVC has a difference with H.264/AVC. Core coding technology included in the one profile of the HEVC includes hierarchical coding structure technology, conversion technology, quantization technology, in-screen prediction coding technology, inter-screen motion prediction technology, entropy coding technology, loop filter technology, and other technologies in a total of eight fields.
Table 1 shows the international standard history of scalable video coding (SVC) technology such as the HEVC.
TABLE 1StandardAdoptionSVC standardYearOrganizationin IndustryMPEG-21996ISO/IECHardlyVideo, H.262MPEG, ITU-TVCEGMPEG-4 Visual1999, 2002ISO/IEC MPEGHardlyH.264/AVC2007ISO/IECVideo conferenceMPEG, ITU-Tsystem, imageVCEGsecurity system, etc.HEVC2014ISO/IECStill unsettledMPEG, ITU-TVCEG
As shown in Table 1, current HEVC scalable extension is fourth SVC codec standard and has been standardized in July, 2014. Since the HEVC scalable extension needs a correction of a standard document and a reference SW bug and a codec implementation process in industry, it is predicted that the HEVC scalable extension is to be actually used from 2016. Since previous three-time SVC codec is not actively used in industry, standardization has been made for overcoming a failure of conventional SVC standard. In comparison with the H.264/AVC, a high implementation complexity of the SVC standard is determined as a cause of an adoption rate which is low in industry, and the HEVC scalable extension has minimized an implementation complexity.
In this case, the SVC denotes a complex bitstream image where various kinds of images are included in one bitstream, and may provide an image service in various networks and dissimilar terminal environments by compressing various kinds of images into one complex bitstream.
However, although the next-generation image coding technology has been developed and requirements for an UHD broadcast service are rapidly increasing, a related art UHD broadcast service is transmitted over only a dedicated broadcast network, causing the inconvenience of a user of a mobile terminal when the user desires to receive the UHD broadcast service such as HD, 4K-UHD, 8K-UHD, etc.
Moreover, relevant technology is being developed for preferentially gaining next-generation broadcast technology all over the world, and high efficiency broadcast service technology for providing a broadcast service in a fixed environment and a mobile environment is needed.